I think Luke is fine with the playbook. They raved about how much of the playbook he learned right away when he came in. If I were to guess they are trying to just get him comfortable in game situations, which he is already showing that he can play.I agree with this point, although it is somewhat skewed by the relentless, my-God-this-play-again? use of the tight end screen last year.
Also, I'm afraid that if Frost inserts McCaffrey as the starter, yards per attempt will sink even lower. If Luke's going to start, they need to remove the training wheels and give him more of the playbook to work with.